WASHINGTON — Months before the Justice Department asked that a citizenship question be included in the next census, researchers were hearing concerns about the survey's confidentiality, based largely on the administration's immigration policies.

Census Bureau researchers who have been working on the technology to be used in the 2020 Census have been testing questions on volunteers, and the researchers reported that the volunteers had “spontaneously” raised concerns about who would have access to information about immigration status at higher rates than in the past.

The volunteers mentioned the “Muslim ban” and expressed "discomfort registering” the demographic characteristics of other household members. They also brought up the administration's decision to end Deferred Action for Childhood Arrivals, better known as DACA, the Obama-era program that protected young immigrants brought to the country as children from deportation. Volunteers made repeated references to Immigration and Customs Enforcement (ICE), according to a Sept. 20 memo and a Nov. 2 presentation.

Some participants provided false information on the people they lived with because of these fears. The behavior was exhibited even though the volunteers were being paid and had established rapport with their interviewers.

“It should be noted that this level of deliberate falsification of the household roster and spontaneous mention of concerns regarding negative attitudes toward immigrants, is largely unprecedented,” one memo stated.

The Justice Department's request that a question about citizenship be on the 2020 Census, made in a Dec. 12 letter, was first reported and posted online by Pro Publica. The department argued that adding the question would help protect voting rights. The request was made by the general counsel for the Justice Management Division, which advises the department on department policy.

But the request is raising concern that even merely asking about citizenship status, and the publicity surrounding the request, will raise fears among some respondents.

To some critics, the request is an extension of the department’s hard-line approach on immigration and an attempt to create a mindset in parts of the population that the 2020 Census could be used to turn them or their family members over to immigration officials.

Groups such as the Central American Resource Center, Carecen, based in Washington, have for many years organized campaigns and helped the Census Bureau find numerators from the community who could persuade immigrants to fill out census forms. About 74 percent of Americans mailed back their census forms in 2010.

Abel Nuñez, Carecen's executive director, said his group tries to explain to people that the law prohibits the Census Bureau from sharing the information with other parts of the government, except in formats for statistical research.

“In previous administrations, you could count on the executive office to make that clear, but with this administration … They may want that confusion to continue to be out there because it benefits their immigration strategy,” Nuñez said.

The Census Bureau said in a statement that it is evaluating DOJ's request and handling it the same as it has past requests. The bureau said that its final list of questions must be submitted to Congress by March 31, and that Wilbur Ross, the secretary of the Commerce Department, which oversees the Census Bureau, will then make a decision.

"Our top priority is a complete and accurate 2020 Census," the bureau said.

The bureau referred to that statement when asked by NBC News whether it had concerns that asking about citizenship would lead to hesitancy to respond, and whether adding the question would increase costs.

Devin O'Malley, spokesman for the Justice Department, said in a statement that the department is "committed to free and fair elections for all Americans and has sought reinstatement of the citizenship question to fulfill that commitment." Other NBC News questions on the request were not addressed.

For the past year, since the administration began its immigration crackdowns, advocates and community leaders have been warning immigrants not to open their doors to people they don't know and in particular to law enforcement. They've advised immigrants to require law enforcement to slip warrants signed by a judge under their doors. Those warnings were mentioned by Spanish-speaking volunteers to the Census researchers testing the survey.

“The undocumented community is going to be very hesitant to open the door to an agent of the government seeking information about their family,” Nuñez said.

Silvia Navas, who was undocumented when the 2000 Census was taken, said that her instinct at the time was to avoid answering questions.

“My first approach to that was not doing it. I didn’t think it would help me very much,” said Navas, now a citizen who works with Casa, an immigration advocacy group. “I was not documented and being in hiding was the best thing to do.” She couldn’t recall if she ultimately filled out the form.

Mark Hugo Lopez, director of Hispanic research at the nonpartisan Pew Research Center, said a question about citizenship hasn’t been on a short census form, which is sent to most Americans, since 1820. Questions have been asked since then about parents’ birthplace, but not about citizenship, he said.

A citizenship question was on the 2000 census long form, but that form was replaced by the American Community Survey, an ongoing questionnaire that helps decide the distribution of hundreds of billions of dollars in federal funding. A citizenship question is on that survey, which is sent to about 3.5 million U.S. households.

There has been debate for years about including a citizenship question on the decennial census, but Congress — which plays a role in approving questions — has been more interested in questions about ancestry than birthplace, Lopez said.

Steve Murdoch, who was U.S. Census Bureau director under President George W. Bush, said the primary mandate of the census is to provide a product to be used to redistrict Congress. Many state legislatures also use the data to draw political boundaries for elections.

The House has 435 members from districts with average populations of 710,767, based on the 2010 Census. (Every state gets two U.S. senators.) Undocumented immigrants, legal residents, children, the homeless and the incarcerated are included in the population counts for political district boundaries.

DOJ said that the current census data on citizenship is inadequate for collecting information on voting age population, which it says is needed to prevent racial discrimination in drawing districts.

Arturo Vargas, a member of the Census Bureau’s National Advisory Committee, called the administration’s request “perplexing” and its voting rights arguments for adding the question “ridiculous.” The civil rights community has not been asking for such a question to be added to bolster voting rights, he said.

Framing it as necessary to enforce voting rights "is coming out of left field — or right field," Vargas said, referring to conservatives who have pushed for counting only citizens for political representation.

Vanita Gupta, president and CEO of the Leadership Conference on Civil and Human Rights, has asked Ross to reject the DOJ request.

Gupta, who headed the DOJ's Civil Rights Division under President Barack Obama, said in a letter to Ross that census estimates have been "suitable" for enforcing civil and voting rights and continue to be.

She said DOJ's justification for a citizenship question being added to the census should be viewed skeptically "as an attempt to throw a wrench into final planning and preparations" of the 2020 Census "that already faces enormous challenges, including inadequate and delayed funding, cybersecurity risks and a climate of fear fanned by anti-immigrant rhetoric.”

Ali Noorani, executive director of the National Immigration Forum, said in a statement the request is meant “to scare immigrants into not responding, which will make them less represented in redistricting."

Related

The Census Bureau also has been working on how to ask Americans about their race and ethnicity, particularly in how it asks about Latino identity, and on including new questions on race and ethnicity for people with Middle Eastern and African roots. The early December deadline for the administration to announce its decision on the questions, based on recommendations from the Census Bureau, has passed without an announcement.

By law, states must consider minority populations in drawing political districts and ensure the districts they draw do not suppress minority voting rights. The more people are counted, the more they will be included in congressional representation.

Lopez said that if the question requested by DOJ is included and the Census gets lower response rates, it may have to send more numerators door-to-door to get people to respond, which would cost more. At this time, funding for the Census 2020 is the same as it was in 2010, Lopez said.

“This has been a concern for Census 2020 to keep costs down. That’s why the bureau has introduced a number of changes in the way it will be done in order to reduce cost, relative to 2010,” he said.

Murdoch, now a professor of sociology at Rice University in Houston, said the Census Bureau is now at a point in the process where it has to make some decisions on the final product and move forward.

“Anything that delays that, limits or changes the amount of resources needed for completion, certainly is a concern,” he said.